Industrial shredding equipment is known and used, for example, in the recycling industry, to break apart large objects into smaller pieces that can be more readily processed. In addition to shredding material like rubber (e.g., car tires), wood, and paper, commercial shredding systems are available that can shred large ferrous materials, such as scrap metal, automobiles, automobile body parts, and the like.
FIG. 1A generally illustrates an example shredding system 100 as is known and in use in the art, and FIG. 16 illustrates a more detailed view of a conventional shredding head or rotors that may be used in such a shredding system. More specifically, as shown in FIG. 1A, this example shredding system 100 includes a material inlet system (such as chute 102) that introduces the material 104 to be shredded to the shredding chamber 106. The material 104 to be shredded may be of any desired size or shape, and, if desired, it may be heated, cooled, crushed, baled, or otherwise pretreated prior to introduction into the shredding chamber 106. If necessary or desired, the inlet system 102 may include feed rollers or other machinery to help push or control the rate at which the material 104 enters into the chamber 106, to help hold the material 104 against an anvil 108, and/or to help keep the material 104 from moving backward up the chute 102. A disc rotor is shown, however, other rotors, such as spider and barrel, are also commonly used, and this invention may be equally useful with those types of rotors.
A rotary shredding head 110 (rotatable about axis or shaft 110A) is mounted in the shredding chamber 106. As the head 110 rotates, the shredding hammers 112 extend outward and away from the rotational axis 110A of the head 110 due to centrifugal force (as shown in FIG. 1A). As they rotate, the shredder hammers 112 impact the material 104 to be shredded between the hammer 112 and the anvil 108 (or other hardened surface provided within the shredding system 100) in order to break apart the material 104. The construction of one conventional shredding head 110 will be described in more detail below in conjunction with FIG. 16. As the material 104 is shredded, it may be discharged from the shredding chamber 106 through one of the outlets 114a provided in a discharge grate 114 located along the bottom and side of the chamber 106 walls, and transported in some manner (generally shown by arrows 116, such as via gravity, via conveyors, via truck or other vehicle, etc.) for further processing (e.g., further recycling, reclamation, separation, or other processing).
FIG. 1B provides a more detailed view of an example shredding head 110 that may be used in the shredding system 100 of FIG. 1A. This example shredding head 110 is made from multiple rotor disks 120 that are separated from one another by spacers 122 mounted around the drive shaft 110A. While any number of rotor disks 120 may be provided in a shredding head 110 (e.g., 8-16), this illustrated example includes seven disks 120 (the end disk 120 is omitted from FIG. 16 to better show the details of the underlying structures). The disks 120 may be fixedly mounted with respect to the shaft 110A (e.g., by welding, mechanical connectors, etc.) to allow the disks 120 to be rotated when the shaft 110A is rotated (e.g., by an external motor or other power source, not shown). In addition to providing a spacing function, spacers 122 can help protect the shaft 110A from undesired damage, e.g., due to contact with material 104 being shredded, broken parts of a shredder hammer 112, etc.
Hammer pins 124 extend between at least some of the rotor disks 120 (more commonly, between several disks 120 and/or through the entire length of the head 110), and the shredder hammers 112 are rotatably mounted on and are rotatable with respect to these pins 124. More specifically, as shown in FIG. 1B, a hammer pin 124 extends through an opening 112A provided in the mounting portion 112F of the shredder hammer 112, and the shredder hammer 112 is capable of rotating around this pin 124. In this illustrated example, the shredding head 110 includes six hammer pins 124 around the circumference of the rotor disks 120, and a single shredder hammer 112 is provided on each pin 124 between two adjacent rotor disks 120 (such that each hammer pin 124 includes a single shredder hammer 112 mounted thereon and such that the shredder hammers 112 are staggeringly distributed along the longitudinal length of the head 110). This hammer pattern may be modified as required by the end user, depending on their needs. At locations between rotor disks 120 where no shredder hammer 112 is provided on a particular hammer pin 124, the pin 124 may be covered with a pin protector 126, to protect the pin structure 124 from contact with and damage caused by the material 104 being shredded. These pin protectors 126 may be of any desired size and/or shape.
In use, the rotor disks 120 are rotated as a unit with shaft 110A, e.g., by an external motor or other power source (not shown). The centrifugal force associated with this rotation causes the shredder hammers 112 to rotate about their respective pins 124 to extend their heavier blade ends 112E outward and away from the shaft 110A, as shown in FIG. 1A. As the rotation continues, the shredder hammer 112 will contact the material 104 to be shredded. Because it is rotatably mounted on the hammer pin 124, contact with the material 104 to be shredded may cause the shredder hammer 112 to slow down or even rotate in the opposite direction as it smashes the material 104 to be shredded against the anvil 108. The pins 124, pin protectors 126, hammers 112, spacers 122, and rotor disks 120 may be structured and arranged so that, in the event that a shredder hammer 112 is unable to completely pass through the material 104, it can rotate to a location between adjacent plates 120 and thereby pass by the material 104 until it is able to extend outward again under the centrifugal force due to rotation of the shredder head 110 about shaft 110A for the next collision. Also, in some instances, the shredder hammer 112 will shift sideways on its pin 124 as it passes by or through the material to be shredded.
If desired, the various parts of the shredder head 110 may be shaped and oriented with respect to one another such that a shredder hammer 112 can rotate 360° around its pin 124 without contacting another pin 124, a pin protector 126, the drive shaft 110A, another hammer 112, etc. Shredding systems and heads of the types described above are known and used in the art.
Thus, as described above, the reduction (e.g., shredding) is achieved by introducing the material 104 to be shredded into the path of the rotating hammers 112 (located within a drum or housing), and the accompanying impact with the hammers 112 alone is enough to achieve at least partial reduction. Further reduction may occur as the hammers 112 force the material 104 across and through the discharge grate 114. The discharge grate 114 is webbed or has a sieve-like structure including a plurality of discharge openings 114a. The openings 114a in grate 114 can be of any pattern, but conventionally the openings 114a are aligned in both circumferential and axial rows. When the reduced fragments of input material are small enough, they pass through the grate openings 114a and leave the machine. The discharge grate 114 has a high wear rate and, as a sacrificial component, has to be replaced frequently. The discharge grate 114, however, does not wear as fast as the hammers 112, which must be replaced more frequently.
Features of conventional or known discharge grates 114 will be described in more detail in conjunction with FIGS. 1C through 1K. As shown in FIG. 1C, the bottom and side portions of this example discharge grate 114 (e.g., extending approximately 80° to 250° around the circle defined by rotary motion of the shredder head 110) are made from a plurality of separate discharge grate components 130 aligned around a portion of the circumference of the circle. Five individual discharge grate components 130 are shown in the example of FIG. 1C. The discharge grate components 130 include a structure that engages with a corresponding structure provided on a mounting frame 132, e.g., associated with the shredder housing, drum, or other reduction machine, to mount the discharge grate components on the frame 132. The discharge grate components 130 are individually abutted against the mounting frame 132 and slid (or otherwise moved) along the frame rails to the desired location in the overall discharge grate structure 114 (e.g., using a crane or other lifting equipment).
FIGS. 1D through 1K show various views of an individual discharge grate component 130, including a bottom perspective view (FIG. 1D), a top perspective view (FIG. 1E), a top view (FIG. 1F), an end view (FIG. 1G), a front view (FIG. 1H), and cross sectional views (FIG. 1I-1K) taken along line B-B in FIG. 1H. As shown in these figures, this discharge grate component 130 includes two longitudinally oriented grate elements 136a and 136b with a plurality of transverse grate elements 134 extending between the longitudinal grate elements 136a and 136b. The grate discharge openings 114a are defined between the longitudinal grate elements 136a and 136b and the transverse grate elements 134 to provide the sieve or webbing structure to the interior working surface 134S of the grate component 130 (see FIG. 1E). The outer sides of longitudinal grate elements 136a and 136b include portions of transverse grate elements 134 that will be used to form portions of grate discharge openings 114a with adjacent discharge grate components 130 when the plurality of grate discharge components 130 are mounted around the mounting frame 132.
As shown in these figures, longitudinal support beams 138a, 138b are provided in this grate component structure 130 as integral extensions of the longitudinal grate elements 136a, 136b, respectively, that form edges of the grate discharge openings 114a. The longitudinal support beams 138a, 138b in this illustrated example have an arched structure that extends outward (away from working surface 134S) and has greater height at the center of the longitudinal direction as compared to its height at the edges (near ends 140). This feature provides support against deformation and bending at the longitudinal center area (and the frames 132 at the longitudinal ends 140 of the grate component 130 help provide additional support against deformation and bending at locations near the ends 140). Because of the presence of longitudinal support beams 138a, 138b, as perhaps best shown in FIG. 1D, the longitudinal grate elements 136a, 136b extend outward (and away from working surface 134S) beyond the outer surfaces 134a of the transverse grate elements 134 in this structure 130. At least one of the longitudinal support beams (138a, in this illustrated example) may include one or more handle elements 142 to better enable lifting and handling of the grate component 130, e.g., by a crane. Longitudinal support beam shapes other than arched are possible, such as rectangular or trapezoidal shapes.
As shown in FIG. 1I, the discharge opening 114a is oriented at an angle α with respect to a direction normal N to the interior working surface 134S of the webbing structure defined by the longitudinal grate elements 136a and 136b and the transverse grate elements 134. In conventional discharge grate components 130, this angle α is typically within a range of about 0° to 30°. The discharge angle helps better accept the reduced material within discharge opening 114a as the material is moving under the rotary force of the rotating hammer structure. Notably, however, for discharge grate components 130 located more on the side areas of the grate circle (e.g., area S shown in FIG. 1C), the extended longitudinal support beams 138a, 138b can provide a relatively long shelf on which discharged materials can get hung up during operation of the reducing equipment. This hang-up problem is further exacerbated by the solid construction of the support beams 138a, 138b. 
The longitudinal support beams 138a, 138b oppose the direct force of the hammer 112 impacts and incorporate a substantial support structure to counter these impact loads. The support beams 138a, 138b constitute a significant portion of the mass of the grate component 130. As illustrated in FIG. 1J, however, because of the desired discharge angle α and the fact that the longitudinal support beams 138a, 138b are integrally formed extensions of the longitudinal grate elements 136a, 136b, the direction of greatest grate strength of the longitudinal support beams 138a, 138b (shown by arrows 144 in FIG. 1J) is angled from the direction of impact force from the hammers (shown by arrows 146 in FIG. 1J, e.g., in a direction normal to the interior working surface 134S of the grate component structure 130). If these directions 144, 146 get further away from alignment (i.e., if angle β gets too large), this may lead to distortion or deflection of the grate component 130 and/or even to failure of the grate component 130. Distortion or deflection of the grate components 130 can lead to decreased performance due to decreased impact energy imparted by the hammers to the scrap and/or difficulty in removal of these components from the frame (e.g., increasing the need to trim or cut the grate to remove it from the mill). In an effort to combat distortion, deflection, or breakage, the longitudinal support beams 138a, 138b are made with the arched structure as described above, and at an angle of no more than about 30 degrees. This feature, however, further increases cost and weight of the overall grate component structure 130.
As noted above, this existing design of longitudinal support beams 138a, 138b on grate components 130 are structurally oriented to account for the direction of flow of the material exiting the mill through the discharge openings 114A. Because the longitudinal support beams 138a, 138b of existing grate components 130 are not aligned with the impact direction of the hammers, they are not optimally positioned to provide the best resistance to bending and deflection. This orientation can result in the beams 138a, 138b (and/or grate elements 136a, 136b) bending tangentially (e.g., in the circumferential direction) rather than outward from the drum. When bent or warped tangentially, the bent beam(s) may interfere with adjacent beams 138a, 138b and/or grate components 130 and/or with the mill housing or frame 132 so that on refurbishment, the grate components 130 become jammed and have to be cut out of the mill or can damage the mill housing. Bent beams 138a, 138b and/or bent grate elements 136a, 136b also can impede flow of material through discharge channels 114A and/or result in plugging the channels 114A. Also, beam support material located away from the impact surface 134S of the grate component 130 is bulky and inefficient, resulting in unnecessary throw-away weight/scrap material after service.
As is evident from the above description, grate components 130 are exposed to extremely harsh conditions of use. Thus, grate components 130 typically are constructed from hardened steel materials, such as low alloy steel or high manganese alloy content steel (such as Hadfield Manganese Steel, containing about 11 to 14% manganese, by weight). Such materials are known and used in the art. Even when such hardened materials are used, however, the surface 134S of the grate components 130 facing the hammers 112 wears significantly and the grate components 130 are replaced on a regular basis to maintain production rates. The balance of the grate components 130 (e.g., the outer surfaces and structures, including beam supports 138a, 138b) experience much less wear and serve as support structures that are subsequently scrapped when the interior working surface 134S becomes excessively worn. FIG. 1K generally illustrates portions of a typical grate component 130 that may be scrapped when the useful life of the grate component 130 has ended (e.g., the top portion of the grate component 130 shown in FIG. 1J will have been largely ablated and worn away after significant use). As is evident from FIG. 1K, significant portions of the beams 138a, 138b and grate elements 136a, 136b, 134 may be scrapped.
Accordingly, there is room in the art for improvements in the structure and construction of grates for reducing equipment.